Subject: | Re: [TowerTalk] Actual LP Performance vs Tribanders |
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From: | Jim Smith <jimsmith@shaw.ca> |
Date: | Thu, 29 Jul 2004 22:21:14 -0700 |
List-post: | <mailto:towertalk@contesting.com> |
Hmm... This would appear to have severe ramifications for tuning the 40m
portion of my C4SXL. F12 has a tuning procedure on their web site which
involves adjusting the jumpers on the linear loading wires to achieve
best F/B and then adjusting the hairpin for best SWR. I live on a 33 x
120 ft city lot. The C4 will be up about 50 ft which handily clears all
the nearby roof tops but not the trees lining the streets or the HV
power line running down the lane at 50 ft. I was planning on asking a
nearby ham (a mile or two) to provide a signal for tuning purposes.
There's all kinds of clutter between him and me, he's about 200 ft lower
in elevation than me and his antenna is quite low. Sounds like this
isn't a good idea. Maybe I could take my HP3400A AC VTVM (good up to 10 MHz or so - should be fine for 40m relative measurements) with a small (tuned?) loop a block or two away and use it as a field strength meter. The elevation would be about 30-40 ft below the C4. Line of sight other than some tree foliage. Could do the same with the 706, I guess, but would be giving up a lot in relative FS measurement accuracy. Then again, I could connect the 3400A across the Tx feed line, adjust the Tx output for constant S meter reading on the 706 as the beam is rotated (a la N4ZR) and note the 3400A reading. Presuming that the MkV minimum output is 1W then I'd have a 23 dB range of adjustment. More than enough for this purpose. Another possibility would be to enlist the help of a ham who lives on the side of a mountain across a body of water from me. I think his elevation might be higher than mine by 100-200 ft. I'd guess he's about 10 miles away, certainly more than 5. Another possibility would be to use a GDO to set the resonant frequencies of the DE and reflector and then just adjust the hairpin for best SWR. Anybody know what those frequencies would be for a contester who wants to operate cw, phone and RTTY and has the 40m relay box for phone operation? This requires knowing the desired DE resonant frequency for when the relay is both energized (cw band) and de-energized (phone band). I gather that I would want the reflector tuned to a frequency below 7.000 so it doesn't turn into a reflector when I'm at 7.001. I've got an Autek RF1. Could I use that somehow instead of the GDO? I do know that min SWR does not necessarily indicate the resonant frequency so tuning the elements for min SWR referred to 50 ohms clearly won't work. I would be very appreciative of any comments or suggestions as to how to proceed with tuning the C4SXL on 40, given the constraints of my situation. Sorry for the staleness of this. Haven't had time to keep up with this reflector for some time. Getting there, though, only 1,050 more posts to read (not counting other reflectors). 73 de Jim Smith VE7FO Tom Rauch wrote: At 03:44 AM 6/26/2004, Peter Sundberg wrote:have seen the _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk |
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